Separate ResponseActions from ClientHttpRequest

Before this commit RequestMatcherClientHttpRequest served both as
API to define request expectations, i.e. ResponseActions, as well as
the implementation of ClientHttpRequest representing actual requests.

DefaultResponseActions replaces this class as a simple holder of
expected requests and mock responses. MockRestServiceServer is then
responsible to match request expectations and create a mock response.

Issue: SPR-11365

spring-test/src/test/java/org/springframework/test/web/client/MockClientHttpRequestFactoryTests.java

@@ -52,10 +52,8 @@ public class MockClientHttpRequestFactoryTests {
 	@Test
 	public void createRequest() throws Exception {
 		URI uri = new URI("/foo");
-		ClientHttpRequest expected = (ClientHttpRequest) this.server.expect(anything());
 		ClientHttpRequest actual = this.factory.createRequest(uri, HttpMethod.GET);
 
-		assertSame(expected, actual);
 		assertEquals(uri, actual.getURI());
 		assertEquals(HttpMethod.GET, actual.getMethod());
 	}